Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0011570 (depression)
 172,036 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Involvement of the brain serotonin (5-HT) neurotransmitter system in obsessive-compulsive disorder (OCD) was originally suggested on the basis of therapeutic effects found with the semiselective serotonin uptake inhibitor, clomipramine. More recent studies directly comparing clomipramine with non-selective or norepinephrine-selective uptake inhibitors, such as desipramine or nortriptyline, as well as studies with new, more selective serotonin uptake inhibitors, including fluvoxamine and fluoxetine, have supported that hypothesis. Clomipramine's antiobsessional effect has been augmented with the serotonin precursor, L-tryptophan, or with lithium, which has prominent serotonergic effects. Patients whose OCD symptoms improved on clomipramine worsened when the drug was discontinued (regardless of duration of therapy) and improved when clomipramine was reinstituted. OCD symptoms also worsened when metergoline, a 5-HT antagonist, was given to patients who had improved with clomipramine. Metergoline given alone had no effect. Administration of m-chlorophenylpiperazine (m-CPP), a 5-HT receptor agonist, to untreated OCD patients increased their anxiety, depression, and dysphoria, and exacerbated their OC symptoms. After 4 months of clomipramine therapy, m-CPP failed to produce the same behavioural effects, suggesting an alteration of a 5-HT subsystem (possibly downregulation of some 5-HT receptors). The data reviewed suggest an important role for an abnormal brain 5-HT subsystem in patients with OCD.
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PMID:Obsessive-compulsive disorder as a 5-HT subsystem-related behavioural disorder. 269 36

Various irregularities in serotonin (5-HT) function have been postulated as causes of affective disorders. Serotonin has been related to many of the major symptoms of depression, e.g. mood, appetite, sleep, activity, and cognitive dysfunction. Interference with 5-HT synthesis or storage has been shown to induce depression in vulnerable individuals. Decreased levels of 5-hydroxyindoleacetic acid (5-HIAA) in cerebrospinal fluid, decreased plasma tryptophan, low tryptophan neutral amino acid ratio, abnormalities in serotonergic function indicated by neuroendocrine challenge tests and various platelet measures, have been reported in depressed patients. Concentrations of 5-HIAA, the major metabolite of 5-HT in plasma, were found to be significantly negatively correlated with severity of depression as measured by the Hamilton Rating Scale for Depression score and specific depressive symptoms, despite the fact that plasma 5-HIAA is largely peripheral in origin. Blood platelets, which have been suggested as models for serotonergic nerve terminals, have a significantly decreased number of 5-HT uptake sites and 3H-imipramine binding sites in depressed patients. Antidepressant drugs may act, in part, by enhancing serotonergic activity. The serotonergic deficit may occur at any of several levels: diminished availability of precursor, impaired activity of tryptophan hydroxylase, abnormalities in 5-HT release or uptake, 5-HT receptor abnormalities or interactions with other neurotransmitters.
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PMID:Serotonergic dysfunction in depression. 269 37

Identification of 5-HT receptor subtypes--5-HT1A, 5-HT1B, 5-HT1C, 5-HT1D, 5-HT2 (possibly A and B), 5-HT3 subtypes, and possibly 5-HT4--has encouraged the manufacture of 5-HT receptor inhibitors with greater subtype specificity. However, it appears that the receptors interact, and drugs initially thought to be specific may have multiple actions. For some conditions such as anxiety/depression, almost all receptors are implicated. Clinical studies provide clear evidence that manipulation of the 5-HT system has a role in treating depression, anxiety, obsessional illness, migraine, and eating disorders. Interactions between the various receptor subtypes make it difficult to identify specific clinical functions. The 5-HT1A receptors may be involved in aggression, anorexia, and hypotension. The 5-HT1B receptors may be involved in aggression, while the 5-HT1C receptors may play a role in central aversion systems and anxiety/depression. The role of the 5-HT1D receptors remains speculative; 5-HT2 receptors appear to be involved in depression, anxiety, appetite, sleep, vasoconstriction, and hypertension. Many drugs that are effective in treating migraine are potent 5-HT2 antagonists. 5-HT3 antagonists at high doses are effective in treating nausea and at low doses in treating anxiety. Treatment of aggression, suicidal behaviour, addiction behaviour, memory impairment, dementia, and schizophrenia with 5-HT inhibitors requires further testing.
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PMID:Is there a relationship between serotonin receptor subtypes and selectivity of response in specific psychiatric illnesses? 269 41

Serotonin (5-HT) increases impulse activity in visceral afferent C-fibers in vivo. A 5-HT-induced membrane depolarization may partially account for this effect. Here, we examined the potential contribution of an additional mechanism to the 5-HT-mediated increase in impulse activity. Approximately 40% of rabbit visceral C-fiber neurons exhibit a protracted (greater than 3 s) spike afterhyperpolarization (AHPslow) that is a major determinant of repetitive firing properties in these neurons. Intracellular recording methods were applied to rabbit nodose ganglion neurons in vitro to assess whether 5-HT could increase excitability through effects on the AHPslow. Results revealed a concentration-dependent 5-HT-mediated depression of the AHPslow amplitude and duration that was accompanied by decreased accommodation of action potential firing. Experiments with 5-HT receptor antagonists further showed that this autacoid depressed the AHPslow through a different 5-HT receptor subtype than that subserving the 5-HT-induced depolarization. Thus the AHPslow represents a distinct locus where 5-HT can increase the impulse activity of these visceral C-fiber afferents.
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PMID:Serotonin increases excitability of rabbit C-fiber neurons by two distinct mechanisms. 279 60

The pharmacological activity of N-[2-(2,6-dimethoxyphenoxy) ethyl]-2-(2-methoxyphenoxy) ethanaminium chloride (ACC-7513) was determined in isolated smooth and cardiac muscle and its effect on blood pressure and heart rate assessed in the spontaneously hypertensive rat (SHR). ACC-7513 was found to be a potent alpha-adrenoceptor blocking agent (pA2:8.33) and a 5-hydroxytryptamine (5-HT) antagonist (pA2:7.01), both in rabbit aortic strips. The affinity for alpha-adrenoceptors was about 20 times greater than that for 5-HT-receptors. High concentrations of ACC-7513 did not block histamine in rabbit aortic strips, or beta 1- or beta 2-adrenoceptor responses induced by isoprenaline in guinea-pig right atria and trachea, respectively, but did block cholinoceptor responses induced by carbachol in rat uterus, non-competitively. High concentrations of ACC-7513 also produced sino-atrial depression in guinea-pig right atria and direct relaxation of depolarized rabbit aortic strips. ACC-7513 depressed blood pressure of conscious SHRs and produced a reflex increase in heart rate. The reductions in pressure were modest and of short duration. It is concluded that: (a) ACC-7513 is a potent, selective alpha-adrenoceptor and 5-HT receptor antagonist; and (b) ACC-7513 is not likely to be useful in the treatment of hypertension.
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PMID:Pharmacological activity of ACC-7513, a selective alpha-adrenoceptor and 5-hydroxytryptamine receptor blocking agent. 286 Sep 40

All results presented here would indicate that serotonin plays an important role in animal behavior such as locomotor depression and that, taking into consideration the effects of antidepressants on 5-HT receptor activity as well as recent biochemical findings of human depression, some forms of human depression could be induced by a cerebral serotonergic receptor hyperactivity contrary to a conventional theory of serotonin deficiency in the synaptic cleft in the brain.
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PMID:Serotonin metabolism of animal model of depression. 617 20

The hypothesis of an etiopathogenic role of 5-HT and that of a mediation by the 5-HT system in the effect of antidepressant treatments have often been confused. Little unequivocal evidence exists for a 5-HT deficit in depression. However, several recent animal and clinical data suggest that the 5-HT system might contribute to the therapeutic effect of various antidepressant treatments. Long-term administration of tricyclic antidepressant (TCA) drugs induces a sensitization of rat forebrain neurons to iontophoretically-applied 5-HT. Repeated electroconvulsive shocks result also in an increased sensitivity of forebrain 5-HT receptors. However, chronic administration of a new antidepressant drug, zimelidine, a potent and long-lasting 5-HT uptake blocker, fails to modify 5-HT receptor sensitivity. These results suggest that enhancement of 5-HT neurotransmission obtained via either pre- or postsynaptic mechanisms might determine the antidepressant effect of these treatments. In a recent clinical study, we observed that lithium administration to TCA-resistant depressive patients induced a rapid relief of depression. It is possible that the presynaptic enhancing effect of lithium on the 5-HT system might unveil the TCA-induced sensitization of the postsynaptic 5-HT receptors. Most depressed patients exhibit marked diurnal variations of mood. Preliminary experiments in rats revealed that the responsiveness of hippocampal neurons to iontophoretically-applied 5-HT is enhanced in the evening. Similar diurnal variations of 5-HT receptor sensitivity might occur in human brain and be related to diurnal variation of mood in depression. Since normal individuals do not show these fluctuations of mood, it is proposed that the "mood regulating system" might become 5-HT dependent in depressed patients.
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PMID:Enhancement of the 5-HT neurotransmission by antidepressant treatments. 627 Mar 17

The effects of intracarotid (i.c.) injections of 5-hydroxytryptamine (5-HT; 1-50 micrograms) on carotid chemoreceptor activity recorded from the carotid sinus nerve have been studied in anaesthetized cats. Three separate components in the complex response of the chemoreceptors to injected 5-HT were identified. Firstly, a transient burst of activity was obtained during the injection period in 56% of the recordings. Secondly, in all the recordings a period of chemodepression commenced a few seconds after completing the injection and was usually dose-related. Thirdly, a delayed longer-lasting chemoexcitation occurred in many experiments, concomitant with a fall in systemic blood pressure. The neuronal 5-HT receptor antagonist MDL 72222 (10-100 micrograms kg-1, i.c.) virtually abolished the transient chemoexcitation evoked during 5-HT injections and also significantly increased the mean ID50 for 5-HT-induced chemodepression; in 37% of recordings 5-HT caused a dose-related chemoexcitation after the high dose of MDL 72222. Neither the delayed chemoexcitation nor the hypotension caused by 5-HT were much affected by the antagonist. MDL 72222 itself had a biphasic effect on chemosensory discharge, causing depression followed by a delayed excitation. The 5-HT2-receptor antagonist ketanserin (100 micrograms kg-1, i.c.) had no appreciable effect on the transient chemoexcitation evoked during 5-HT injections and caused a slight but significant increase in the mean ID50 for 5-HT-induced chemodepression. The delayed chemoexcitation and accompanying hypotension associated with 5-HT were both substantially reduced or abolished by the antagonist. Ketanserin itself caused a short-lasting period of chemoexcitation. All the effects of injected 5-HT on chemosensory discharge could be abolished by the combination of MDL 72222 and ketanserin (100 micrograms kg-1, i.c.). Neither MDL 72222 nor ketanserin had any significant effect upon the response of the carotid chemoreceptors to hypoxia. The rate at which discharge increased, and also the steady-state discharge before and during hypoxia, were unaffected by the antagonists, alone or in combination. At least two types of 5-HT receptor appeared to be involved in the response of carotid body chemoreceptors to 5-HT. Transient excitation and chemodepression were mediated via MDL 72222-sensitive (peripheral neuronal) receptors whereas the delayed chemoexcitation and associated hypotension involved a ketanserin-sensitive, presumably 5-HT2-, receptor. It appears unlikely that 5-HT plays a crucial role in chemoreception.
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PMID:Effects of the antagonists MDL 72222 and ketanserin on responses of cat carotid body chemoreceptors to 5-hydroxytryptamine. 648 93

The serum cortisol concentration following administration of 5-hydroxytryptophan (5-HTP), 200 mg orally, a precursor of serotonin (5-HT), was significantly greater in unmedicated depressed and manic patients than in normal controls. Increases in serum cortisol levels greater than 5 micrograms/dL were significantly more frequent in both unmedicated depressed and manic patients than in the normal controls. There was significant test-retest reliability. Baseline serum cortisol concentration correlated negatively with the cortisol response to 5-HTP in normal controls. These results suggest increased 5-HT receptor sensitivity may be present, possibly in the hypothalamus or pituitary, in some patients with affective disorders. These results are consistent with the hypothesis that decreased serotonergic activity, which would be expected to produce increased 5-HT receptor sensitivity, may be present in both depression and mania.
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PMID:Effect of 5-hydroxytryptophan on serum cortisol levels in major affective disorders. I. Enhanced response in depression and mania. 660 35

The ability of antidepressant drugs, electroconvulsive treatment (ECT), or lithium chloride (LiCl), to modify prolactin secretion in the rat was studied. Chlorimipramine, citalopram, fluoxetine, imipramine and zimelidine potentiated the low dose 5-hydroxytryptophan (5-HTP)-induced increase in prolactin secretion, suggesting inhibition of serotonin (5-HT) uptake by these drugs. Amitriptyline, doxepin, iprindole, mianserin and trazadone inhibited the prolactin stimulating effects of high doses of 5-HTP and quipazine, suggesting that these drugs have 5-HT receptor blocking properties. Tandamine inhibited only 5-HTP-induced increase in prolactin secretion. Chronic administration of imipramine, potentiated the effect of low dose 5-HTP significantly more than an acute dose. Amitriptyline, produced similar inhibition of the 5-HTP-induced increase in prolactin secretion after both acute and chronic administration. The ability of bupropion and mazindol to inhibit alpha-methylparatyrosine-induced prolactin secretion, and of nomifensine to inhibit reserpine-induced prolactin secretion, is consistent with other evidence that these agents are indirect dopamine (DA) agonists. Desipramine, acutely, had no effect on any of the above paradigms but after chronic administration, potentiated the effect of low dose 5-HTP on prolactin secretion. Nortriptyline had no effect on prolactin secretion after acute or chronic treatment. ECT for 10 days did not affect the ability of a 5-HT agonist or d-amphetamine to modify prolactin secretion. However, chronic, but not acute, treatment with LiCl markedly enhanced the prolactin response to 5-HT agonists and reserpine while shifting the dose response curve for d-amphetamine and apomorphine to the right. These results are discussed in light of current theories of the role of 5-HT and DA in depression.
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PMID:Effect of antidepressants, lithium and electroconvulsive treatment on rat serum prolactin levels. 697 60


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